package leetcode.year2021.month10;

/*
21. 合并两个有序链表
 */

public class _10_03MergeTwoLists21 {
  public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
    if (l1 == null) {
      return l2;
    }
    if (l2 == null) {
      return l1;
    }
    ListNode dummy = new ListNode();

    ListNode curr = dummy;

    while (l1 != null || l2 != null) {
      if (l1 == null) {
        curr.next = l2;
        l2 = l2.next;
      } else if (l2 == null) {
        curr.next = l1;
        l1 = l1.next;
      } else if (l1.val > l2.val) {
        curr.next = l2;
        l2 = l2.next;
      } else {
        curr.next = l1;
        l1 = l1.next;
      }
      curr = curr.next;
    }

    return dummy.next;
  }

public class ListNode {
  int val;
  ListNode next;

  ListNode() {
  }

  ListNode(int val) {
    this.val = val;
  }

  ListNode(int val, ListNode next) {
    this.val = val;
    this.next = next;
  }
}

/**
 * 将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。
 * <p>
 * 输入：l1 = [1,2,4], l2 = [1,3,4]
 * 输出：[1,1,2,3,4,4]
 * 示例 2：
 * <p>
 * 输入：l1 = [], l2 = []
 * 输出：[]
 * 示例 3：
 * <p>
 * 输入：l1 = [], l2 = [0]
 * 输出：[0]
 * <p>
 * 来源：力扣（LeetCode）
 * 链接：https://leetcode-cn.com/problems/merge-two-sorted-lists
 * 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
 */
}
